# how to understand the permissible voltage and current of film capacitor?

I use the 0.12uF metallized polyester film capacitor Model ECQE2124JB which has 250VDC rated voltage. I have a sine wave across the capacitor, then can I think that the maximum AC voltage is 250/1.414=176.8 Vrms? But from the characteristic datasheet, the permissible voltage is less than 40Vrms at sinewave. What's the difference? If I use the capacitor in a LC resonant circuit, does it mean the RMS resonant voltage cannot exceed 40Vrms?
In my opinion, the permissible current is calculated as I = 2*pifC*V, for my application f = 10KHz, so I = 2*3.14*10kHz*0.12uF*250V=1.884Ap = 1.33Arms. Is it right? But from the characteristic datasheet, the permissible current is only about 0.2Arms. Why that?
In my LC resonant application, the mearsured current across the capacitor reaches 3.5Arms, but the peak voltage will not exceed 250VDC. It also conflicts with Vrms = Irms *Xc, where Xc is the impedance of the capacitor.

• You can't exceed the permissible voltage or the permissible current or your capacitor might die. It's that simple. Really. Commented Jul 24, 2018 at 4:50